In the field of sports and wide-area lighting, manufacturers are attempting to find ways to make the use of light-emitting diodes (LEDs) competitive where high-intensity discharge (HID) lighting has traditionally been dominant. LEDs can be made more competitive by increasing their lumen output, improving efficacy (lumens per watt), increasing longevity, and reducing cost. Thus, any technology that has the potential to improve on one or more of these factors is desirable in the lighting industry.
Certain techniques for improving individual factors are well known in the industry; however, improving one factor may diminish other factors. For example, LEDs are typically rated for lumen output @ 25° C. and 350 mA. Increasing current increases lumen output, but lowers efficacy at the same temperature; still worse, when temperature increases as is typical with increased power input, efficacy and lumen output decrease.
Likewise, LEDs can have a much longer average life than other types of lighting (e.g., on the order of 50,000 hours versus 5,000 hours); however, average life is reduced significantly as the LEDs are operated at higher temperatures and currents. LED life can be reduced by one or two orders of magnitude by operating at higher currents and temperatures that are still considered to be within viable operating parameters (e.g., 1000 mA and 125° C.). This can reduce their usability for lighting applications requiring thousands of hours per year of ON time, but is not necessarily a liability for lower usage applications such as some types of sports lighting (which may require as little as 250 hours of ON time per year).
The cost for fixtures and support structures is a very significant part of LED lighting cost. Reducing the number of LEDs required per fixture to achieve a given light level on a target area can significantly lower overall costs; however, reduction of the number of LEDs requires increasing light output per LED, which results in reduced average life due to higher currents and operating temperatures.
Therefore, managing LED temperature is important to optimizing efficiency, efficacy, and cost. Thus, there is room for improvement in the art.